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Edge Nitrogen Out of Water

Edge Nitrogen Out of Water
Edge-of-field practices take water out of tile drainage water before it leaves the farm.

By Lynn Betts

A majority of farmers are trying to manage nitrogen more efficiently for better crops and to cut the amount that leaves their farm. At the same time, a few farmers are going the extra mile to install edge-of-field practices specifically to take water out of tile drainage water before it leaves the farm.

Edge-of-field practices can each reduce N losses 30% to 50%.

While in-field nitrogen management practices like side-dressing and applying only the amount of nitrogen plants can use cut N losses by up to 10% per practice, the edge-of-field best management practices each cut N losses by 30% to 50%. The have a place in Iowa's Nutrient Reduction Strategy, says Matt Lechtenberg, the Water Quality Initiative Coordinator for the Iowa Department of Agriculture and Land Stewardship.

"We need to pair in-field and off-field practices for a cumulative effect," Lechtenberg says. "We want producers to have all the tools they need to be successful, both in advancing environmental stewardship and in being profitable."

Hypoxia action plan
The Iowa strategy -- based on voluntary farmer actions -- was developed in response to the 2008 Gulf Hypoxia Action Plan that calls for 12 states along the Mississippi River to develop strategies to reduce nutrient loading to the Gulf of Mexico. The Gulf Action Plan sets a goal of at least a 45% reduction in total nitrogen and phosphorus loads in water reaching the Gulf of Mexico.

Keegan Kult, the Environmental Projects Manager for the Iowa Soybean Association, conducts a monitoring program for ISA to assess the impacts of best management practices on water quality. He's also working on a USDA-NRCS conservation innovation grant looking to help Iowa farmers install edge-of-field practices to reduce nitrogen loads from tile water before it leaves their farms.

"Iowa is a big contributor to the nitrate levels in water feeding into the Gulf of Mexico," Kult says. "There's no question we need tile to optimize production in many fields," he adds. "Unfortunately, those tile lines can carry high nitrate-N loads. There are half a dozen practices we're assisting with and monitoring for effectiveness in reducing N loading."

Kult is monitoring 20 bioreactors the ISA helped install, and is working with farmers on such practices as wetlands and drainage water management. He's also helping evaluate restored oxbows.

The idea of some of the practices is to keep the water in the soil profile longer, to reduce the total amount of water leaving the farm, which reduces the amount of nitrogen leaving. In other BMPs, such as the bioreactors, wetlands, and oxbows, water is stored long enough for wood chips or plants to denitrify the nitrates. The table on this page gives more information on how each BMP works and how much nitrate-N it can remove from water.
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